Selenium is a trace mineral that is found in soil, and an essential micronutrient for horses. How can you tell if your horse is receiving enough selenium, and are there signs of a selenium deficiency in horses? Although horses only require an FDA recommended 3mg of selenium per day, many horses will require a supplemental source. Even though selenium is a naturally occurring mineral, some regions have micronutrient deficiencies in the soil. Unlike horses, humans have more options for selenium intake, including nuts, fish, some meats, and grains.
Role of Selenium in Horses
Horses need selenium for optimal cellular function. In conjunction with vitamin E, selenium acts as an antioxidant protecting healthy cells and maintains the proper circulation of thyroid hormones.
Oxidizing agents known as free radicals attack lipids, creating lipid peroxides. The antioxidants help protect from or prevent lipid peroxides from forming, and help prevent damage to cell function.
Selenium also boots a horse’s natural immune response. Although only small quantities are needed, selenium is essential.
Signs of Selenium Deficiency in Horses
Although symptoms can be far-ranging, there are distinct signs of selenium deficiencies. One of the most notable problems that can develop from a deficiency is white muscle disease. This is a degenerative disease that can affect multiple forms of livestock and their skeletal and cardiac muscles.
Foals and developing horses are more susceptible if their nursing mothers lack selenium. Foals with white muscle disease may develop fast heart rates, struggle to swallow or suckle, or have discolored dark urine.
Selenium deficiencies may also cause horses to “tie-up” due to rhabdomyolysis (frequently accompanied by dark urine).
Less severe but important symptoms include poor coat and hoof quality, muscle soreness, decreased performance, or decreased fertility.
Correcting Selenium Deficiency in Horses
Selenium intake should be monitored, especially when supplementing specifically for this trace mineral. Extremely high doses of selenium will cause acute toxicity and possibly death, but these cases are very rare.
More commonly, horses lack selenium-rich forage due to soil conditions and require adding the mineral into their diets.
A deficiency can be diagnosed with a simple blood test by your veterinarian, and easily corrected with over-the-counter supplementation, feed, or different forage sources. Some manufacturers of salt and mineral blocks also produce blocks with added selenium. However, acute deficiencies may require injectable medication to instantly boost selenium levels.
Checking Your Resources
Most commercial feeds and grains contain small amounts of selenium. Regardless of whether you suspect a selenium deficiency, horse owners can test their soil and hay for micronutrients.
Although more common tests for forage include crude protein and acid detergent fibers, analysis of trace mineral content is also available. Some regions have known selenium deficiencies in their soil. However, areas like Montana, are known for selenium-rich soils. It’s no surprise that forage from these areas tends to have higher selenium levels than the national average for similar grass hays.
For more information on forage and soil testing, you can contact your local agriculture extension agency. Extension representatives and your local equine veterinarian are also good resources to help you better understand the nutrition breakdown on your commercial feed labels.
Due to the toxicity potential, selenium has been labeled as an environmental hazard despite the necessity for optimal cell function in horses. Therefore, there are government regulations on selenium content in commercial feeds. Luckily, there are multiple products on the market that can help add adequate amounts of selenium into horses’ diets. However, horse owners still need to be mindful of how much selenium is being supplemented. Most selenium supplements are accompanied by added vitamin E.
These are some of our top picks available on Amazon:
- This formula includes vitamin E and selenium for optimal immune support and antioxidants. Vita E & Selenium Crumbles is available in a 3lb and 20lb (a 640-day supply!) and provides 1mg of selenium per half an ounce. This is a good option to monitor selenium intake by singular milligram in cases where the horse may already be consuming some selenium. This is yet another winning formula from the makers of Red Cell.
Also, find it in horseloverz.com
- If it can be supplemented, AniMed makes it! Their Vitamin E and Selenium comes in a 2.5lb or 5lb bucket, and also contains zinc. Each powder tablespoon of product contains approximately 625IU of vitamin E and 1.4mg of selenium. The powder is a great feed topper, or perfect for picky eaters when easily mixed with something enticing!
Also, find it in horseloverz.com
- The UltraCruz Equine Selenium Yeast supplement contains organically chelated selenium in powder or pelleted formula. Two manufacturer-recommended scoops of product contain 2.4mg of selenium. The powder formula is a simple no-fuss topper, and the pelleted formula is an alfalfa meal and flaxseed base.
- Farnam delivers yet again! Vita-Min E & Selenium offers 625IU of vitamin E and 1mg of selenium per .5 oz serving. A modest 3lb bucket will last 96 days at the standard serving suggestion!
Although the FDA recommended dosage of selenium for horses may seem small, selenium is a powerful necessity in your horse’s diet. It is important to examine feed, pasture, and added forage for selenium content.
If there is a suspected deficiency, contact your equine veterinarian for plasma, serum, or whole blood selenium level test. Likewise, if your horse is exhibiting dangerous symptoms of selenium toxicity, these tests can also reveal the current selenium measurements. Your local extension agent will also have information on known soil conditions of your region, which can provide a wealth of knowledge on micronutrient consumption in grazing horses.
Do you live in a selenium-rich or deficient area? Have you ever needed to have soil or forage testing done? Let us know what (or if) you’re supplementing, and be sure to share this article with your horse friends!